#include <bits/stdc++.h>
using namespace std;
int main() {
  double dis = 0;
  double len = 2;
  int step = 0;
  double s;
  cin >> s;
  while (dis < s) {
    dis += len;
    step++;
    len = len * 0.98;
  }
  cout << step;

  return 0;
}